This invention relates to the transmission of digital multimedia communication information to end user subscribers via bandwidth limited circuits, and more particularly to digital subscriber line (DSL) network transmission.
The quest to make television a truly interactive medium has spurred technical development in the transmission of digital video. Heretofore, technical development in this arena focused primarily on digital data network connectivity and specifically on connectivity to the Internet. This prior focus on network bridging for video on demand (VoD), Internet access, and digital compression technology is in part driven by the perceived notion of maintaining compatibility with conventional bus type cable television plants.
The connectionless network paradigm, which serves as the basis of the Internet, does not commit network resources to particular conversations as is done in circuit switched networks. Rather, it is based upon a packet switching paradigm in which all information travels across a connectionless network without a specified route. While this paradigm is ideally suited to the world of “bursty” information delivery, applications such as digital video distribution require the capability to specify minimum bandwidth, controlled response times, and other Quality of Service (QoS) parameters inherent to a circuit switched paradigm. Known mechanisms for specifying the QoS needed are rudimentary at best in the connectionless network model. As a result, current connectionless, “best-effort” technological paradigms are not suited for true switched video applications.
Switched circuit technology stands as a promising alternative. Switched network technology serves as the basis of the public switch telephone network. In switched networks, conversations take place via a dedicated channel path established between the two conversing parties. This permits the quality of service of the network connection to be guaranteed. Switched circuit communication is typically performed via a twisted pair line terminating in simple jack in the subscriber's household, but the underlying technology is suited to fiber optic, coaxial cable and wireless connections up to the end user. For example, leading edge development in the switched network arena has produced the Asynchronous Transfer Mode (ATM), a high speed, multiprotocol, fiber optic network. ATM accommodates high bandwidth applications requiring certain QoS minimums, such as desktop video conferencing, imaging and voice transmission.
Internet Protocol (IP), the ubiquitous workhorse protocol of the Internet, has gained widespread popularity due to its universal compatibility with virtually any network design. The field of end-user interface devices or so-called “settop” arena has also embraced IP technology. For example, vendors of settop units such as Stellar One Corporation of Seattle, Wash. and Acorn Computer Company (a.k.a. Online Media) of Cambridge, England have produced “IP-aware” settop units. Internet IP compatibility is a highly desirable feature for providing the seamless integration of television, Internet, videophone and telephone services.
One notable problem with using switch circuit technology for the distribution of digital video is that bandwidth is typically limited in digital subscriber line circuits to about 4 MPBS downstream to the end user and approximately 640 KBPS upstream. In light of the foregoing, what is needed is a technique for distributing digital video information as well as Internet access and telephone information over a limited bandwidth medium using the switched circuit paradigm.